DESCRIPTION (Taken directly from the application) Mortality in patients undergoing dialysis in the U.S.A. is higher than that recorded in Western Europe and Japan, but also is much higher than the mortality in the general age matched population. The current Mortality and Morbidity in Hemodialysis Patients (MMHD) trial has as primary goals the performance of a randomized, prospective, long term trial which will compare two ranges of dialysis dose, the higher being substantially larger than those currently used routinely, and two types of membranes, one removing only small and the other removing both small and large molecular weight substances. The objective of the study is to understand the relationship between dialytic methods and mechanisms of disease in dialysis patients. Dialysis dose measured by the fractional clearance of urea (Kt/V) will be quantified according to double pool kinetics, providing, for the first time in any systematic manner, a true measure of the effectiveness of dialysis therapy. The effects of therapy will be understood by analysis of the outcomes of mortality, hospitalization, cardiac and infectious problems developing during the trial. In addition, the presence of defined study populations facilitates the possibility of ancillary studies aimed at more detailed analysis of, for example, cardiac disease. Special care will be taken to ensure that the study patients are representative of the U.S. population in regards to age, gender, race and diabetes. Underlying all four treatment groups will be adequate protein/calorie nutrition and a uniform standard of general medical care. The results of the trial will provide the basis for effective therapy until the time that the field of renal replacement therapy advances quantitatively or qualitatively by other means. In addition, much experience will be gained concerning the practicality of the new techniques to be investigated that could be applied to the general dialysis population.